This PR implements:
* A new hint: PROPERTY_HINT_NODE_TYPE for variant type OBJECT, which can take specific node types as hint string.
* The editor will show it as a node path, but will set it as a pointer to a node from the current scene if you select a path.
* When scene is saved, the node path is saved, then restored as a pointer.
NOTE: This is a proof of concept and this approach will most likely not work. The reason if that, if the node referenced is deleted, then when trying to edit this the node will become invalid.
Potential workarounds: Since this uses the Variant API, it should obtain the pointer from the Variant object ID. Yet, this would either only really work in GDScript or it would need to be implemented with workarounds in every language.
Alternative ways to make this work: Nodes could export an additional property with a node path (like for which_node, it could be which_node_path).
Another alternative: Path editing could happen as a hidden metadata (ignoring the pointer).
* Ensures thread safety when resources are destroyed.
* Simplified API by always forcing `ResourceCache::get_ref`, which needs less hacks and is fully thread safe.
* Removed RWLock for resources because its not possible to use for the new logic. Should not be a problem.
Supersedes #57533
Clean up and do fixes to hash functions and newly introduced murmur3 hashes in #61934
* Clean up usage of murmur3
* Fixed usages of binary murmur3 on floats (this is invalid)
* Changed DJB2 to use xor (which seems to be better)
These spaces are not needed for the file to be successfully parsed.
Other types such as Vector3 are no longer serialized with spaces
after the opening parenthesis and before the closing parenthesis,
so this is also more consistent.
Fix mistake making `set_custom_format` impossible to use.
Automatically forward custom flags in `SurfaceTool.commit`.
Add documentation in `SurfaceTool` and `Mesh` for custom channels.
Deprecate `SurfaceTool.generate_lod` and expose `ImporterMesh.generate_lods`.
Nearest-neighbor filtering of the heightmap results in a broken
appearance, with and without Deep Parallax enabled on the material.
Linear filtering results in a more expected appearance. This does
not affect other texture maps such as albedo, normal or roughness.
